It was estimated that in 2007, more than 75% of U.S. population was over 18. Today, increasing numbers of adults are seeking orthodontic treatment to enhance the social and psychological status of their life. Treatment of these patients is complicated by the fact that the correction of their malocclusion orthodontically is limited to the dento-alveolar element, since any opportunity for control over their growth and development has passed. While simple cases can be treated by orthodontics treatment alone, the severity of malocclusion in many adults is beyond orthodontics treatment, and can only be addressed through combination with orthognatic surgery. Unfortunately, orthognatic surgery by itself is very expensive, and due to extensive bone cuts in upper and lower jaws can be accompanied by many complications. Therefore at present, there is no other treatment modality for these groups of patients.
It is certainly common for a patient to need an alignment of one or more teeth and, through typically, one method of carrying out such alignment or movement of a tooth is through the use of braces that are installed to the teeth and which include wires and other tension devices, such as rubber bands and coils, to exert a continual tension on the tooth to move the tooth or teeth in to the desired position. One of the problems, however is that the use of braces to move the teeth can take a long period of time, some times 3-4 years, and the patient must continue to wear those braces throughout these long periods. The wearing of braces is sometime difficult for patients, particular adults, who do not like the appearance of the braces and do not like the discomfort. In addition it has been shown that having braces for long time can increase the risk of root resorption and loss of alveolar bone.
One of the reasons for the lengthy period of time is that the tooth needs to move within the jaw bone, which includes the alveolar bone, that contains the tooth sockets, and the cortical plate encasing the dento-alveolar component. In effect, the tooth cannot move until the alveolar bone has been remodeled and that simply takes considerable time. It would therefore be advantageous to have a means to hasten the movement of a tooth or teeth so that the time period to move the tooth or teeth to a desired location is shortened.
Orthodontic cases are generally divided into two categories according to the direction the tooth movements are made, either expansion where crowded and crooked teeth are moved toward the periphery of the outline of the jawbone or retraction where one or more teeth are removed to create more room in the jaw. To align the teeth, one or more teeth may be moved in the direction of spaces created. Conventional orthodontics is performed by moving the root of a tooth through its surrounding bone in the jaw. The bone of the jaw has a hard outer shell, called the cortical plate or cortical bone, and a softer interior called the medullary bone.
The medullary bone has a good blood supply and is highly populated with pluripotential cells that can convert to osteoclasts that resorb old bone and osteoblasts that make new bone. Therefore, the medullary bone responds relatively dramatically and timely to physical insult including the forces used to move teeth. To move a tooth orthodontically, the root of the tooth must be moved through the bone surrounding the tooth, the alveolar bone consisting of the medullary bone and surrounding cortical plates that comprise the upper and lower jaws. The alveolar bone remodels around a tooth being moved in response to pressure and tension around the roots of teeth. In the course of such bone remodeling, bone resorption occurs on the pressure side of the root surface in the direction in which the tooth is moving. Bone deposition or new bone formation occurs on the tension side of the root surface in the direction away from which the tooth is being moved.
The root of a typical tooth is usually so large in diameter that it occupies most of the space between the lingual cortical plate on the inside of the jaw and the facial cortical plate on the outside of the jaw. As a result, much of the root of a tooth is covered with hard cortical plate and with very little soft medullary bone.
A major drawback to conventional orthodontics is the long treatment time during which braces must be worn. Corticotomy has been used for several decades to attempt to shorten orthodontic treatment times. The term refers to a bony cut or perforation that extends through the entire thickness of the cortical plate of the alveolus and into the underlying medullary bone or, if no medullary bone is present under the cortical plate, it refers to a bony cut or perforation that extends through most of the thickness of the cortical plate, but not its entire thickness.
Fischer et al., Angle Orthod 2007; 77:417-420 propose that instead of orthognatic surgery, small cuts be made in the alveolar bone around the teeth, a process that is known as corticotomy. It would be desirable if this highly invasive corticotomy procedure can be simplified even further and replaced with minimal, shallow, small perforations in alveolar bone without need for soft tissue flaps (as required with corticotomies).
Corticotomy has been used in difficult adult cases as an alternative to conventional orthodontic treatment or orthognathic surgery. It has been claimed that by combining a corticotomy procedure with orthodontics, it is possible to complete treatment in a shorter period of time due to the ability to move teeth more rapidly. The mechanism of this action is not clear. Several authors have described rapid tooth movement observed in conjunction with corticotomy as movement by “bony block.” Based on this concept, a fissure is made through the cortical plate that surrounds a tooth, so that this tooth will now be in a block of bone connected to surrounding bone only through the medullary bone. The tooth is the “handle” by which this block of bone can be moved. Others have related the effect of corticotomy-facilitated orthodontics to the repair mechanism that is observed following injury of bone. After bone injury, accelerated bone turnover and decreases in regional bone density have been described.
Scott, U.S. Pat. No. 7,329,122 and Scott, U.S. Patent Publication No. 2008/0102415 teach using flapless corticotomy using long needles. This procedure requires fabrication of a guide to determine the best places for application of cortical perforations. Scott proposes using needles to produce deep and narrow perforations that may be damaging to tooth roots and surrounding tissues. To compensate for this side effect, Scott designed a complex template as a guide for safe application of multiple cortical plate perforations. This technology makes the application of these procedures very difficult and unpractical.
Wilcko et al., U.S. Pat. No. 6,109,916 teaches extensive cortical plate perforations requiring full thickness mucoperiosteal flap and bone grafting. These procedures are rather excessive to accelerate tooth movement. In addition they are extremely uncomfortable, time consuming, and expensive, involving different specialists. They also pose a significant risk for infection, rejection of bone graft, gingival recession, and bone loss. Some references describing this and similar procedures include for example, Yen S et al., J Oral Maxillofac Surg 61:1346-1350; 2003; Iino S et al., Am J Orthod Dentofacial Orthop 131: 448.e1-448.e8; 2007; Liou et al., Am J Orthod Dentofacial Orthop 117:391-8; 2000; Hwang et al., Am J Orthod Dentofacial Orthop 120:209-16; 2001; Germec D et al., Angle Orthodontist 76:882-890; 2006; Wilcko et al., World J Orthod. 4:197-205; 2003; Wilcko et al., Int J Perio & Rest Dent. 21: 9-19; 2001; and Fischer, Angle Orthodontist. 77-3; 2007.
Orthodontic forces induce an aseptic inflammatory response. During early stages of tooth movement, there is an increase in vascular permeability and cellular infiltration of leukocytes (Krishnan, et al., Am J Orthod Dentofacial Orthop, (2006a) 129:469.e1-469.e32; Meikle, Eur J Orthod (2006) 28:221-240). Migrated immune cells along with native cells such as fibroblasts and osteoblasts produce inflammatory cytokines which include lymphocyte- and monocyte-derived factors, colony-stimulating factors, growth factors, and chemotactic factors (Krishnan et. al., J Dent Res (2009) 88(7):597-608; Ren, et al., Eur J Oral Sci (2008) 116(2):89-97). High concentrations of inflammatory cytokines such as interleukin-1 (IL-1), IL-2, IL-3, IL-6, IL-8, tumor necrosis factor-α (TNFα), interferon-γ (IFNγ,) and osteoclast differentiation factor have been found in the gingival crevicular fluid surrounding moving teeth (Alhashimi et al., J Interferon Cytokine Res (2000) 20(1):7-12; Garlet et al., Eur J Oral Sci (2007) 115(5):355-62; Ren et al., J Periodontol (2007) 78(3):453-8).
The role of cytokines during tooth movement is not very clear. It has been suggested that cytokines and other inflammatory markers such as prostaglandin E2 (Saito et al., Am J Orthod Dentofacial Orthop (1991) 99(3):226-40) may activate bone remodeling characterized by bone resorption in the compression region and bone deposition in the tension region of the periodontal ligament (PDL) (Davidovitch et al., Dent Clin North Am (1988) 32(3):411-35; Garlet et al., Eur J Oral Sci (2007) 115(5):355-62). This is in agreement with previous studies that demonstrated that bone injury which causes cytokine release, leads to an accelerated bone turnover and a decrease in regional bone density (Frost, Henry Ford Hosp Med J (1983) 31(1):3-9; Frost, Part II. Clin Orthop Relat Res (1989a) 248:294-309; Frost, Part I. Clin Orthop Relat Res (1989b) 248: 283-93; Shih, et al., Bone (1985) 6(5):377-9; Yaffe et al., J Periodontol (1994) 65(1):79-83). One possible mechanism through which inflammatory cytokines may affect bone remodeling is through recruitment of osteoclast precursors from the circulation, their maturation and activation. Many cytokines that promote osteoclast formation and activation, such as IL-1, IL-6, and TNFα (Glantschnig et al. Cell Death Differ (2003) 10(10):1165-77; Seidenberg, et al., Pharmacol Res (2004) 50(2):151-6; Yao et al., J Biol Chem (2008) 283(15):9917-24), have also been found in crevicular fluid during orthodontic tooth movement (Basaran et al., Am J Orthod Dentofacial Orthop 2006; 130:E1-6; Uematsu et al., J Dent Res. 1996; 75:562-567).
The effect of cytokine expression on bone remodeling is important since the rate of tooth movement correlates with the efficiency of bone remodeling in the alveolar process. Studies of knockout mice deficient for TNFα receptors (Yoshimatsu et al., EJ Bone Miner Metab (2006) 24(1):20-7) showed a slower rate of tooth movement in response to orthodontic forces. Also previous reports showed that anti-inflammatory medication can decrease the rate of tooth movement (Arias, et al., Am J Orthod Dentofacial Orthop (2006) 130(3):364-70).
It would be advantageous to provide methods and devices for assisting tooth movement that provide fewer number and lesser depth of perforations. Likewise, it would be advantageous to provide devices and kits that facilitate performing effective perforations so as to assist tooth movement without the disadvantages of conventional needles.